<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>task18</title>
    <style>
        span{
            display:inline-block;
            height:30px;
            line-height:30px;
            background-color: red;
            color:white;
            margin-right:5px;
            margin-top:10px;
            font-size:24px;
        }
        span:hover{
            cursor: pointer;
        }
    </style>
    <!--<link rel="stylesheet" href="style.css" type="text/css">-->
    <script src="task.js" type="text/javascript"></script>
</head>
<body>
    <input type="text" id="in_put" >
    <input type="button" id="left_in" value="左侧入" onclick="NumLeftIn()">
    <input type="button" id="right_in" value="右侧入" onclick="NumRightIn()">
    <input type="button" id="left_out" value="左侧出" onclick="NumLeftOut()">
    <input type="button" id="right_out" value="右侧出" onclick="NumRightOut()">
    <div id="content"></div>
</body>
</html>